Power unit pressure responsive device



Aug. 26, 1952 E. A. ROCKWELL POWER UNIT PRESSURE RESPONSIVE DEVICE 8Sheets-Sheet 1 Original Filed April 11, 1941 Aug. 26, 1952 E. A.ROCKWELL POWER UNIT PRESSURE RESPONSIVE DEVICE Original Filed April 11,1941 8 Sheets-Sheet 2 g- 1952 E. A. ROCKWELL 2,608,061

POWER UNIfI PRESSURE RESPONSIVE DEVICE E. A. ROCKWELL POWER UNITPRESSURE RESPONSIVE DEVICE Original Filed April 11, 1941 8 Sheets-Sheet4 Iii Aug. 26, 1952 E. A. ROCKWELL POWER UNIT PRESSURE RESPONSIVE DEVICE8 Sheets-Sheet 5 Original Filed April 11, 1941 Aug. 26, 1952 OriginalFiled April 11, 1941 E. A. ROCKWELL 2,608,061

POWER UNIT PRESSURE RESPONSIVE DEVICE 8 Sheets-Sheet 6 Aug. 26, 1952 E.A. ROCKWELL 2,608,061 POWER UNIT PRESSURE RESPONSIVE DEVICE OriginalFiled April 11, 1941 8 Sheets-Sheet 7 Aug. 26, 1952 E. A. ROCKWELL2,608,

POWER UNIT PRESSURE RESPQNSIVE DEVICE Original Filed April 11, 1941 8Sheets-Sheet 8 v 2 58 57 11w Z57 gYyUM'l m Patented Aug. 26, 1952 UNITEDSTATES PATENT ()FFICE POWER UNIT PRESSURE RESPONSIVE DEVICE EdwardRockwell, Shaker Heights, Qhio Original application April 11, 1941,Serial No.

388,002, now Patent No. 2,448,464, dated August 31, 1948.

Divided and this application June 5, 1946, Serial No. 674,508

18 Claims.

My invention relates particularly to the confurther object is to provideeffective valve means for the application of power, by means of fluidpressure. Another object is to provide a grommet valve construction foreffectively controlling the inlet and outlet of a pressure diiieringfrom the atmospheric pressure, for the operation of the power unit.Another object is to'provide an effective hydraulic cut-oh? valve meansin a construction in which manual pressure is first ep- 7 plied,followed .by the application of power under the control of the firstmentioned pressure. Another object is to provide a power unit having apiston motor therein for operating a pressureincreasing plunger, thesame being arranged in an effective manner with means to convey a vacuumto the power unit initially for submerging the piston therein :with theaid of an external vacuum pipe connecting the ends of the power unit.Another object is to provide a hydraulic connection extending outside ofthepower unit, for delivering from the power'unit a low pressure withoutthe aid of power, followed by a power pressure. Another object is toprovide a head portion for the power unit having a hydraulic inlet portand a hydraulic outletdelivery port as Well as a hydraulic port for thecontrol of the power unit. my invention will appear from the detaileddescription of the same hereinafter.

While my invention is capable of embodiment in many different forms, forthe purpose of illustration I have shown only certain forms thereof inthe accompanying drawings, in ,which Fig. l is a plan view of a .powerunit system made in accordance with my invention, taken partly insection 'on line l-l of, Fig. 3;

Fig. 2"is an end elevation of the same;

Fig. 3 is an elevation of the other end of the same with the coverremoved;

Figs. 4 and 4A show a viewfin a longitudinal section of the same takenon line .4--4.-of'Fig. 2 and 4- of Fig. 3;

Fig. 5 is a plan view of .amodi'fied form of my invention;

Fig. 6 is an end elevation of the same, taken partly in section on line6-6 of Fig. 5;

Further objects of Fig. 7 is an elevation of the otherend of the same;

Figs. 8 and 8A show a vertical section of the modification shown in Fig.5;

Fig, 91 is a diagrammatic arrangement of the 1 system including my powerunit, for example the embodiment shown in Figs. 1 to 4A thereof;

Fig. .10 is a horizontal transverse section showing a slightly differentarrangement of the differential plunger and housing therefor;

Fig. 11 is an end elevation of another modified form of reactionplungerthat may be used; and

Fig. 12 is a longitudinal section of the same r taken on line ,l2- |2 ofFig. 11.

, Referring first to the form of my invention shown in Figs. 1. to 4Aand 9, I have shown'a pedal! mounted. on a lever 2 which is pivoted on ashaft '3 carried by a chassis of an automobile, not shown. A link 4 isattached to said lever 2 intermediate its ends so as to give any desiredpedal ratio movement of the pedal -l-' to the brake-operating link 4.The'said link '4 is pivotally connected to an operating lever 5 of amastercylinder 5 which may be any desired io'rm of 'vnaster cylinde'rbut,"for example, such as disclosed in the patent to Loug'head et al.No.

"1,707,063, granted'March 26, 1929. "Thelever 5 "is carried ona shaft 1passing into the master cylinder 6, which has an arm 18 for operatinga'piston'Q carried in a cylinder Ill within a storage chamber ll havinga vent l2 and a filler cap 13'. When the pedal is moved downwardly the'piston 9 is adapted to discharge the liquidof the master cylinder froma flexible pipe 14 to an inlet opening fitting l5 screw-threaded inavalve casing it which in turn is screw-threaded in a 'head piece orcasting I! secured by screws [8 to an end closureflS which is welded toan outer casing 20 having'two pairs of ridges 2| and 22,

between the ridges of each pair of which they .are located 'straps'23and 24 respectively. Each of the straps f has horizontal end portions 25ing 31 to receive a -screw 32 arranged to pass through any desiredpartof the chassis frame for supporting the power unit. The liquid, uponbeing received from the master cylinder into the opening [5, initiallypasses through-apassageway 33 and thence past a valve Seat and outthrough openings .35, in the 'valve casing l6.

' From this point the liquid passes out through an opening {35 to afitting 3'! connected to a flexible pipe 38 which 'leads'to brakecylinders "39 arranged'to operate brake shoes -El carried withinbrakedrums on the automobile wheels.

3 The said pipe 38, by branch pipes, may lead to all four wheels in thisway. A plug 42 normally closes the 'third available outlet for theliquid from the opening 36. The provision of the three outlets, wherethe fittings 31, 4I and plug 42 are located, enables the connectionsfrom the power unit to be readily adapted to the brakes irrespective ofthe different possible locations of the power unit on the chassis. Theliquid from the master cylinder thus initially passed to the brakes,will move the brake shoes up into position preparatory to the latterapplication of power thereto for the main braking effect. Simultaneouslywith this initial application of the hydraulic liquid to the brakes thehydraulic liquid will be conveyed through a port 43 in the valve casingI6 to an annular chamber 44 on the outside thereof and thence by apassageway 45 to a fitting 46 connected by a pipe 41 within the outercasing 29 to a fitting 48 screw-threaded in a casting 49 which issecured by screws 59 to a ring I welded to the outside casing 29. Thesaid fitting 48 has a pipe 52 connected thereto which conveys thehydraulic liquid to an angular fitting 53 which is screw-threaded into aplunger housing 54 so as to convey the liquid by a passageway 55 to acentral passageway 59 in said plunger housing. The central passageway 59is closed by a screw-threaded plug 51 having a reduced central extension58 to act as a stop for a plunger head 59, but in such a manner as toleave said head 59 exposed to the The said plunger head 59 has aU-shaped rubber seal 99 in a recess BI in a stem 62 connected to saidhead. Thesaid stem 62 has an internal screw-thread 63 so as to receive ascrew-threaded end 64 of a stem 65 attached to a smallerdiameter plunger65 reciprocable within a smallerdiameter continuation 91 of said centralopen ing 55. A U-shaped rubber seal 98 is located in a recess 69 aroundsaid stem 65. Between the said seals 69 and 68 there is thus formed achamber 19 for transmitting at all times the reaction from the liquidapplied to the brake to the manual means. This chamber 19 is connectedby a passageway H to. an opening 12 in the plunger housing 54, havingtherein an angular screwthreaded fitting 13 which in turn is connectedby a fitting 14 to a pipe 15 which passes rearwardly on the inside ofthe outer casing 29 and terminates'in a, fitting 16 screw-threaded intothe casing I1 so as to connect said pipe 15 with the opening 39 for theliquid which is conveyed to the wheel brakes. The said chamber 19 alsois connected by a passageway 11 to an air bleeder 18 carrying aremovable screw-threaded plug 19 of any desired construction, forperiodically releasing any accumulated air from the said chamber 19-,

When the brakes are being moved into position, as above referred to, theincreasing manual pressure from the mastei cylinder moves the plunger 66rearwardly, be-

fore-the power is applied, so as to close a disc-v shaped outlet valve89, said valve 89 being tightened on a cylindrical extension BI on theplunger 66, a gasket 82 being provided ina circular recess between theplunger 66 and the extension 8 I. The said outlet valve 99' is locatedwithin a V vacuum chamber 83 which is connected by a transversepassageway 84 to a longitudinal passageway 85 in the casting 49 andthence to the interior of the outer casing 69 which is at all timesprovided with a vacuum by means of a vacuum inlet port 86 in aring-shaped seat 89a.

The ring 8601. is located in a check valve casing 91 headed into anopening 98 in the'end cover I9, said casing having within the same acheck valve 89 with peripheral serrations 99 to readily permit thewithdrawal of air during the intervals of suction, which is applied by afitting 9I screwthreaded into said casing 91, having connected thereto avacuum pipe 92 which leads to the engine manifold of the automobile orany other suitable source of suction. When moved as above referred to,the outlet valve 89 seats against a rubber diaphragm 93 supported withinthe casting 49, where it is held in place by a ring 94 having peripheralair inlet ports 95 for admitting air from an air inlet port 96 coveredby a screen 91 leading to an air space 98 filled with horsehair in acover 99 having access to the outlet air around its outer rim I99. Thesaid cover 99 is held in place on the plunger housing 54 by means ofscrews WI. The inner periphery of the diaphragm 93 is supported by aring I92 which is fastened by rivets I93 to a spacing ring I94 havingradial ports I95 therein and to a disc-shaped inlet valve I99 alsoseating on said diaphragm 93, and to a supporting diaphragm I9=1 made ofa fabric treated with an oxidized oil, and finally to a dished end plateI98. The outer periphery of said diaphragm I91 is supported between agasket I99 carried on the face of the casting 49 and a cylinder headII9, having a port- III, which is held in place by the screws '59. Thesaid cylinder head II9, furthermore, carries a helical spring II2, theother end of which rests against the ring I92 so as to normally seat theinlet valve I95, and the said head II9 also carries a smaller helicalspring II3, the other end of which seats against a shoulder II4 on theextension BI so as to normally unseat the outlet valve 89. Theincreasing pressure thus applied to the liquid within the pipe 52 will,as it is increased, retain the valve 89 in seated position while bowingthe diaphragm 93 to 'such an extent as to open, as far as desired, the

a disc I29.

air inlet valve I99. Thus, the vacuum which, before the seating'of theoutlet valve 89, has previously entered through the ring I92 and thespacing ring I94 so as to pass through the port III to the right face ofthe cylinder head II9, will actuate a large piston II5 carried within acylinder II6 within the casing 29. The said piston II5 has a leatherring II1 on one face thereof fitting within the said cylinder II6, whereit is retained by a'disc H8, and on the other face thereof a feltlubricating ring II9, carrying lubricating oil initially provided in theapparatus, said ring II9 being held in place by The piston II5, ring II8 and disc I29 are all carried on a piston rod I2I having a head I22 toact as a stop against the cylinder head II9, said rod I2I beingscrew-threaded for attachment thereof to a tubular piston rod I23, whichpasses out through a bushing I24 in a sleeve member I25 to which thereis screwthreaded a cylinder I26.'The other end of the cylinder I26 isscrew-threaded to the casting I1. The said cylinder I26, at its forwardend, is headed over into a cylinder end plate I21 provided with a.vacuum aperture I28. In order to hold these parts together I haveprovided 'a clamping plate I21a. through which bolts I21b pass. Saidbolts, at one end, are screw-threaded into the plate II9 and at theirother ends carry beneath the platev I21 shouldered cleeves I21cextending over the edge of-the "endplate y, I60 in an annular recessI6I.

said chamber I I has a passageway I62 lead ng to I a fitting I63 whichis connected by a pipe I 64 to a passageway I39 to permit thereciprocation therein of a rod I31 having a head I32 which is preventedfrom escaping fromifthefend of the tubular piston rod I23 byprovidingtherein an internal flange I33. The saidrtubular piston rodI23,'furthermore, carries, against the right face of the sleeve memberI25, a ring I34, a U-shaped rubber gasket I35 and an' 'angularpositioning ring I36 which is perforated to prevent an air lock. Thering I34 rests-against a shoulder on the sleeve member I25 and the ringI36fr'ests against a shoulder Within the cylinder 126.. The said rodI3I, at its rear end, has a cylindrical valve I31 screw-threaded theretoand held in place by a lock nut I31a, said cylindrical valve I31 beingprovided with a conical end I38 which is arranged to seat onf'the valveseat 34 which is located in thevalve' casing passageway 33. A coilspring I49fnormally forces .the valve I38 against its seat whenpermitted byv the compression of the spring I29,said spring 7 beinglocated around a reduced extension I on the cylindrical valve I31, .theother end of ,said spring being seated on a disc I42 supported 144 beingprovided in the disc I42.

Inthe form of my invention shown in Figs. 5 to 8A, I have shown amodified form of my invention which is much simpler in construction andwhich can be manufactured at a much lower cost. In this form of myinvention I have shown on the fitting I5,-which leadsjto the mastercylinder II by means of the pipe I4 in the same way as in the previouslydescribed form-of my invention, a valve casing I 6 constructedsubstantially the same as in the previous form of my invention and whichleads by the same passages previously described, to the outlet opening36 in a casting I44a connected to the pipe 38 leading to the brakes forthe operation thereof. In this form of my invention there is apassageway I45 in said casting I44a leading from the inlet I5, to whichthere is connected an angle-fitting I46 having therein a pipeI41. Thispipe I41 leads to a fitting I48 which is screw-threaded into a plungerhousing I49 leading by a passageway I50 to a chamber I5I which is closedvby a plug I52 having a reduced inner end I53 acting as a stop for theleft face of a plunger I54 having a U- shaped rubber seal I55, in anannular recess I56 on said plunger. Said plunger I54 has an internalscrew-thread I51 to receive a stem I53 on a smaller plunger I59 in thechamber I51. The smaller plunger I59 has va U-shaped rubber sealFurthermore, the

fitting I communicating with the outlet openin the screw l61, whichpassageway I69 is normally closed by a removable screw I16. It-wi ll ofcourse be understood that, if desired, the air 'bleed'er 19, shown inconnectionwi-th"the prev 'ious' form of my invention, may be constructedthe same as the air bleeder screw I61 andassociated parts justdescribed. The-smaller plunger I59 has on itsrearface anextension 11-1to which there'is attached an outlet'valve I12; 2.

rubber gasket I13 being provided in anannu'lar I80.' The said grommetI15 also has a rear flange I8I acting as an inlet valve therefor. Inorder to provide freedom of movement and in order to provide an airinlet chamber I82, the grommet I15 is spaced away from the innerperiphery of the ring I19. It will be noted, furthermore, that the ringI19 has transverse passageways I83 for the inlet of airtothe'chamherI82from an outer chamber I84 which communicates with the outer airthrough a peripheral space I85 1 between the ring I19 and theplungerhousing I49. "'Air, which is thus admitted from the chamber I82,when the flange, I8I -.is unseated fromthe ring I19, willfpass 7 throughpassageways I86 provided by 'lugs F81 which support a stop plate I83held in place on the ring I19 by screws I89. The air in this way reachesa space IQII-Withina cylinder1 9l which is supported around a shoulderI92 on the rear face of the ring [19. Within the said cylinderfIBI thereis arranged to reciprocate a piston I93 which supports a leather ring194 having on the front face'of said. ring I94 asupporting disc I95; 0ntherear face of the piston I93 there is afelt lubricating ringl96,

adapted to be provided with a body of lubricating oil'initially. Thesaid felt ring has a supporting disc I91. The 'discs'l95 and I91 and-thepiston I93 are'carried on a screw'l98 having a I head I99 contactingwith the stop plate I88,

and which is screw-threaded into a tubularpiston rod 200 having acentral passageway 20I therein. Theother end of the piston rod 209 isarranged to slide within a bushing 202 in a screw-threaded sleeve 209"head 205 of the cylinderIQI, whichhead" 205 acts as'a support for'astrong helical spring 206,

the other end of which is supported against the disc I91. A vacuum pipe291' leading from the manifoldof the'internal combustion enginescrew-threaded into a, vacuum valve casing 208; having a check valve 299with peripheral 1 notches 2I0, which seats against a valve seat 2IIsupported in the valve casing 208, the latter being'headed over into thecylinder head 295. The vacuum thus communicated to the chamber lei isconveyed to the other end of the cylinder I9I bya' pipe fitting 2I2headed into the cylinder head I9I, into which there is screw-threaded anangle fitting 2I3 connected'by apipe 2I4 to "an angle fitting 2I5screw-threaded into a passageway 2I6 which connects with a vacuumchamber 2I1,, inwhich the outlet valve I12 is located. The rearend ofthe tubular piston rod .200 is provided, at the endofthe sleeve-263',with a ring .2I8adjacent to a U-shaped rubberseal 219, adjacent to whichthere is a ring 229 which isported to prevent an .air lock. The ring2I8rests against the rearend of the sleeve 263': and the ring 220 restsagainst the shoulder within'the cylinder 2B4. Within the central opening2UI there is arranged to reciprocate ahead 22I on a rod 222, said headbeing prevented" from escapingfrom the tubular piston226 byan internalflange 223. The said rod 222, at its'frear end, is screw-threaded to acylindrical: valve member 224, held in place by a lock nut 224a, havinga flexible rubbervalve 225 therein which is arranged to seat againstthevalve seat 34. A coil spring 226 located around a reduced extension 221on the cylindrical valve 224 is'supported at its other end upon a disc228 having a port 229, said disk being supported upona shoulder 239 inthe cylinder 204, which is screw-threaded into the casting I44a.

The cylinder I9I and attached parts to the right thereof are clampedagainst the ring I19 by means of a clamping plate 23I and three bolts232, 233 and 234, which pass throughsaid plate 23I and the ring I19. The=bolt 232 is provided merely with .nuts 235 and 236,,whereas the bolts233 and 234 are longer thanthe bolt 232 and are provided with inner nuts23,1 and 238 which holdthe cylinder I91 and attached parts together,while located outside ofthe'huts 231 and 238 there are brackets 239 and2.4.0 'hav ing holes 24I and 242 for supporting the; power unit from thechassis of the automobile; Nuts 243 and 244 are located on the ends ofthe bolts 233 and 234 in order to fasten the1bolts233 and 234 securelyto the brackets 239and'24ll.

In Fig. I have shown a slightly different form of differential plungerand housing in which it is contained, as compared with the plunger andhousing shown in Figs. 1 to 8. In this figure I have shown adifferentialplunger housing 245 which is constructed in general like "the plungerhousing 54- having the plug 51 therein, the reaction line port H and thefitting 13 communicating with the pipe 15, also-the bleeder port 11 andthe bleeder screw 18 for releasing accumulated air. In the chamber10therein there i is an annular recess 246 in whichthe're is located aflared ring bafile 241 provided with a small port 248 opposite to thebleeder passageway 11 and a large port 249 opposite to the reaction lineport 1 I. The said ring 241 is tightly retained in the recess 246against a shoulder 250 within said chamber 19. A large plunger head 25Ilocated within the chamber 10, has a U-shaped rubber seal 252 in anannular recess 253 therein. The

said plunger 25I has a stem 25hr, provided with a reduced extension 254on which there is carried a rubber seal 255 adjacent .to a small plunger256. On a reduced extension'251 of the plunger 256 there is a gasket 258adjacent to a' head'259 which is screw-threaded on the endofjsaidextension 254. The end of the stem 25Iaserves the same purpose as theend of the extension. BI shown in Fig. 4, to receive one'end ofthespring H3.

In Figs; 11 and 12 I have shown aplunger' 269 that can take the place ofthe'plunger. 59', 66,111 Fig. 1. The plunger 260 islocated in a plungerhousing 26I, having an inlet port 262 whichcan be connected to the pipe52, and a port 263fwhich can be connected to the fitting 13, as'fwell"as flanges 264 and 265' provided with holes266 and 261 to receive screwsfor attachment of'theho'using to the casting 49." This; housing 26I- canbe attached to the cover 99 in any desiredway'but,

for example, in the same way asshowninFig. '1.

Within the housing 26I there is a bore 268 for the plunger260. The saidplunger has an annular recess 269 to receive'a rubber seal 210 andis'provided also with a rubber seal 2', which latter fits over a reducedextension 212 extending through a stationary rubber seal 213, adjacentto a bushing 214 and held in place by a snap ring 215. Beyondthe'extension 212' there is an annular recess 216 to receive a sealingring 211 adjacent to, an enlargement 218 towhich the outlet valve 80 isattached. A small extension 219 receives the spring I I3.

In the operation of the form of my invention shown in Figs. 1 to 4A and9, assuming that the master cylinder II has been provided with a supplyof hydraulic liquid, that the engine is in operation and that it isdesired to operate the brakes, upon moving the pedal I downwardly, thehydraulic fluid will be forced from the master cylinder I I by means ofthe pipe I4 through the valve casing I6 till it reaches the opening 36and is thence discharged by the pipe 38 to the brake system so as toinitially move the brakes into position. At the same time the hydraulicliquid will be conveyed by the pipe 41 to the left face of the plunger59 in the chamber 10 so as thus to seat the outlet valve 80 and unseatthe atmospheric air'inlet valve. I06 to a slight extent, as desired.This initial action in seating the brakes will not be sufficient,however, to start the movement of the piston H5, owing'to the compressedhelical spring I29. At the same time, also, it will be understood thatthe hydraulic liquid from the opening 36 is in communication, by thepipe 15, with the chamber 10 located between the differential plungers59 and 66. Upon further movement of the pedal I, thereby increasing thepressure supplied through the pipe I4, the pressure against the faceofthe plunger 59 will be accordingly increased, thereby resulting inthefurther-opening of the atmospheric air inlet valve I06 whileretaining the outlet valve 80 closed. This position of the valves cuts'oif the vacuumfrom access to the left face; of the piston H5 and admitsatmospheric air from the chamber through the passageways 96,95 and I05to the desired extent, resulting in the movement of the piston pipe-38,thereby applying power for the opera- 'tion of the brakes. 3 At alltimes, however, it will be noted that before and after the applicationof the power the pressure of the hydraulic liquid applied to the brakesis arra'nge'dto react through the pipe 15 on the differential plunger59, 66 so that the foot at all times receives the reaction of the actualpressures being applied-t0 he brakes; It will be noted that the plunger'59 has a larger rear area than the frontface-of the plunger 66 so as toproduce this reaction towards the foot. In this'way, furthermora'the ireaction towards the foot producesan-extreme nicety of control in theapplication of the brakes. Besides, any danger of power lock of'thebrakes,

especially during the range ofhighest power pressures applied'by'theapparatus, is avoided.

However, in any one position in which the pedal I is held in the powerapplication; the admission of the amount of airpermitted to passfrom th9 left face of the valve I06 to the right face thereof will cause thevalve I06 to become seated due to the increase relative pressure on theright face of said valve I06. Also, any hysteresis due to hunting of themovable parts back and forth, is avoided, especially as with thisarrangement it, is not necessary for the foot to be moved too far inchanging from a given pressure applied to the brakes to a slightly lowerpressure application of the brakes. It will be understood, of course,that the relative sizes of the plungers 59 and 66 can be changed as wellas the actual sizes thereof according to the type of vehicle to which itis applied. Upon releasing the pedal I. to release the brakes, the inletvalve I06 becomes seated on the diaphragm 93 and the outlet valve 80 isthen opened, thus giving access of the vacuum to the left face of thepiston H and cutting ofi the same from access to the outer air. Inasmuchas the right face of the piston II5'is always subject to the vacuumandas the left face now has access to the vacuum, the piston H5 will bereturned by the spring I29 to its initial position, resulting in thehead I32 of the rod I3I being moved by the flange I33 on the piston rodI23 towards the left, again unseating the valve I38 and thus place incommunication again the opening I5 and the opening 36, ready forsubsequent manual application of the brakes.

In the form of my invention'as shown in Figs 5 to 8, the'operation takesplace in substanially the same way as just described in connection withFigs. 1 to 4A and 9. In this instance, however, the submergence of thepiston in the vacuum, which in the previous form of my invention isaccomplished by the outer casing 20, is brought about by the pipe 2Mwhich communicates with the two faces of the piston I93. Also, insteadof having two diaphragms, a valve-seating spring and two rigid valvesseating thereon, as in the previous form of my invention, I haveprovided the single rigid out; let valve I12 which seats on the rubbergl'OlIl met I15, the latter serving as a self-closing inlet valve inconnection with the ring I 19 which supports the grommet I15. In otherwords, when the power is being applied from the power unit to the brake,the valve I12 will first become seated upon the grommet I and furthermovement of the valve I12 will push the flange I8| of the grommet I15,acting as an inlet valve, off its seat on the ring I19, thus admittingto the desired extent the air through the passageways I85, I93 andchamber I82, to the left face of the piston I 93, resulting in themovement of the same to apply the power to the brakes in the same way asdescribed in connection with the previous form of my invention; In thisform of my invention, furthermore, I have utilized a somewhat differenttype of valve 225 which is made of flexible rubber, but servessubstantially the same purpose as the conical valve I38 described inconnection with the previous form of my invention.

The operation of the modified form of plunger and housing shown in Fig.10 is substantially the same as the corresponding parts in Figs. 1 to 9.In this instance, however, the ring-shaped baffle plate 241 has beenprovided to permit the bleeding of the air out of the chamber 10,irrespective of whether the bleeder passageway 11 is located at the topor some other radial position with regard to the chamber 10. Thisbecomes useful where for some reason the power unit is desired to beinstalled in different radial 10 positions so far. as the bleederpassageway 11 is concerned. The view in Fig. 10 shows a substantiallyhorizontal section. However, it will be understood that if the bleederport 11 is at the top of the apparatus, the air will readily pass out ofthe chamber 10 through the small hole 248 and passageway 11 when thebleeder screw 18 or I10 is removed. If, instead, the passageway 11happens to be located at the bottom of the apparatus, when air hasaccumulated in the upper portion of the chamber 10,

the removal of the bleeder screw 18 or I10 will cause the air to passaround the outer periphery of the baflie 241 so as to be dischargedthrough the passageway 11. Owing to the relative size of the Openings248 and 249, this air will enter the large port 249 and be dischargedthrough ing a reaction on the foot from the return circuit connected tothe delivery line is a small annular area on which the liquid pressesagainst the pedal pressure and the remainder of the area within saidannulus is the area receiving the main reaction from the brake operatingliquid which is exerted as a reaction back on the pedal through thevalve mechanism.

While I have described my invention above in detail I wish it to beunderstood that many changes may be made therein without departing fromthe spirit of the same.

I claim:

1. A power unit comprising a cylindrical casing forming a low pressurechamber, an inlet for a fluid pressure differing from the atmosphericpressure, a piston in said chamber, hav ing a pressure-increasingplunger connected thereto, adapted to be moved by said pressure, a highpressure chamber for said plunger, an inlet mounted on the outlet end ofsaid highpressure chamber beyond, the end of the plunger for a hydraulicliquid for controlling the powerunit, valve means, located together withsaid hydraulic inlet beyond the end of the plunger and controlled by thehydraulic liquid from the. inlet for controlling the application of saidfluid pressure to said piston, a control plunger arranged to be moved bysaid hydraulic liquid, a delivery outlet, located beyond the same end ofthe plunger for liquid from said plunger chamber connected to saidhydraulic liquid inlet, and a hydraulic conduit leading from saidhydraulic inlet outside of said piston to the control plunger.

2. A power unit comprising a cylindrical casing forming a low pressurechamber, an inlet for a fluid pressure differing from the atmosphericpressure, a piston in said chamber, having a pressure-increasing plungerconnected thereto, adapted to be moved by said pressure, a high pressurechamber for said plunger, an inlet mounted on the outlet end of saidhigh pressure chamber beyond the end of the plunger for a hydraulicliquid for controlling the power unit, valve means, located togetherwith said hydraulic inlet beyond the end of the 1i v plunger andcontrolled by the hydraulic liquid from the inlet for controlling theapplication of said fluid pressure to said piston, a control plungerarranged to be moved by said hydraulic liquid, a delivery outlet,located beyond the same end of the plunger, for liquid from said plungerchamber connected to said hydraulic liquid inlet, a hydraulic conduitleading from said hydraulic inlet outside of said piston to the controlplunger, and a fluid pressure pipe outside said casing leading from oneend of said casing at one side of the movable wallv to said valve meanson the other side of the movable wall.

3. A power unit comprising a cylindrical casing forming a low pressurechamber, an inlet for a fluid pressure difiering from the atmosphericpressure, a piston in said chamber, having a pressure-increasing plungerconnected thereto, adapted to be moved by said pressure, a high pressurechamber for said plunger, an inlet mounted on the outlet end of saidhigh pressure chamber beyond the end of the plunger for a hydraulicliquid for controlling the power unit, valve means, located togetherwith said hydraulic inlet beyond the end of the plunger and controlledby the hydraulic liquid from the inlet for controlling the applicationof said fluid pressure to said piston, a control plunger arranged to bemoved by said hydraulic liquid, a delivery outlet, located beyond thesame end of the plunger, for liquid from said plunger chamber connectedto said hydraulic liquid inlet,'and a hydraulic conduit leading fromsaid hydraulic inlet outside of said piston to the control plunger, saidcasing having secured thereto a head piece containing said high pressurechamber.

4. A power unit comprising a cylindrical casing forming a low pressurechamber, an inlet for a fluid pressure differing from the atmosphericpressure, a piston in said chamber, having a pressure-increasing plungerconnected thereto, adapted to be moved. by said pressure, a highpressure chamber for said plunger, an inlet mounted on the outlet end ofsaid high pressure chamber beyond the end of the plunger for a hydraulicliquid for controlling the power unit, .valve means, located togetherwith said hydraulic inlet beyond the end of the plunger and controlledby the hydraulic liquid from the inlet for controlling the applicationof said fluid pressure to said piston, a control plunger arranged to bemoved by said hydraulic liquid, a delivery outlet, located beyond thesame end of the plunger, for liquid from said plunger chamber connectedto said hydraulic liquid inlet, a hydraulic conduit leading from saidhydraulic inlet outside of said piston to the control plunger, and afluid pressure pipe outside said casing leading from one end of saidcasing at one side of the movable wall to said valve means on the otherside of the movable wall, said'casing having secured thereto a headpiece containing said high pressure chamber.

5. A power unit comprising a cylindrical casing forming a low pressurechamber, an inlet for a fluid pressure differing from the atmosphericpressure, a piston in said chamber, having a pressure-increasing plungerconnected thereto, adapted to be moved by said pressure, a high pressurechamber for said plunger, an inlet for a hydraulic liquid forcontrolling the power unit, valve means controlled by the hydraulicliquid from the inlet for controlling the application of said fluidpressure to said piston, acontrol plunger arranged to be moved by saidhydraulic liquid, a delivery outlet for liquid from said plunger chamberconnected to said hydraulic liquid inlet, a conduit leading from saidhydraulic inlet outside of said casing to the control plunger, saidcasing having secured thereto a head piece containing said high pressurechamber, and a hydraulic liquid cut-off valve movable apart from saidplung- I er, having a stationary valve seat, and operated by the firstmentioned plunger in the high pressure chamber.

6. A power unit comprising a cylindrical casing forming a lowpressure'chamber, an inlet fora fluid pressure differing from theatmospheric pressure, a piston in-said chamber, having apressure-increasing plunger connected thereto, adapted to be moved bysaid pressure, a high pressure chamber for said plunger, an inlet for ahydraulic liquid for controlling the power unit,

valve means controlled by the hydraulic liquid from the inlet forcontrolling the application of said fluid pressure to saidv piston, acontrol plunger arranged to be moved by said hydraulic liquid, adelivery outlet for liquid from said plunger chamber connected to saidhydraulic liquid inlet, a conduit leading from said hydraulic inletoutside of said casing to the control plunger, 3, fluid pressure pipeoutside said casing leading from one end of said casing at one side ofthe movable wall to said valve means on the other side of the movablewall, said casing having secured thereto a head piece containing saidhigh pressure chamber, and a hydraulic liquid cut-oil valve movableapart from said plunger, having a stationary valve seat, and operated bythe first mentioned plunger in the high pressure chamber.

7. A power unit comprising a cylindrical casing forming a lowpressurechamber, an inlet for a fluid pressure differing from the atmosphericpressure, a piston in said chamber, having a pressure-increasing lungerconnected thereto, adapted to be moved by said pressure, a high pressurechamber for said plunger, an inlet for a hydraulic liquid forcontrolling the power unit, valve means controlled by the hydraulicliquid from the inlet for controlling the application of said fluidpressure to said piston, a control plunger arranged to be moved by saidhydraulic liquid, a delivery outlet for liquid from said plunger chamberconnected to said hydraulic liquid inlet, a conduit leading from saidhydraulic inlet outside of said casingto the control plunger, saidcasing having secured thereto a head piece containing said highpressure, and a hydraulic liquid cut-off valve movable apart from saidplunger, having a stationary valve seat, and operated by the firstmentioned plunger in the high pressure chamber to cut off directcommunication between the hydraulic inlet and the delivery outlet.

8. A power unit comprising a cylindrical casing forming a low pressurechamber, an inlet for a fluid pressure difiering from the atmosphericpressure, a piston in said chamber, having a pressure-increasing plungerconnected thereto, adapted to be moved by said pressure, a high pressurechamber for said plunger, an inlet for a hydraulic liquid forcontrolling the power unit, valve means controlled by the hydraulicliquid from the inlet for controlling the application of said fluidpressure to said piston, a control plunger arranged to be moved by saidhydraulic liquid, a delivery outlet for liquid from said plunger chamberconnected to said hydraulic liquid inlet a conduit leading from saidhydraulic inlet out- 13 side of said casing to the control plunger, afluid pressure pipe outside said casing leading from one end of saidcasing at one side of the movable wall to said valve means on the otherside of the movable wall, said casing having secured thereto a headpiece containing said high pressure chamber, and a hydraulic liquidcut-off valve movable apart from said plunger, having a stationary valveseat, and operated by the first mentioned.

plunger in the high pressure chamber to cut ofi direct communicationbetween the hydraulic inlet and thedelivery outlet.

9. A power unit comprising a cylindrical casing forming a low pressurechamber, an inlet for a fluid pressure differing from the atmosphericpressure, a piston in said chamber, having a pressure-increasing plungerconnected thereto, adapted to be moved by said pressure, a high pressurechamber for said plunger, an inlet for a hydraulic liquid forcontrolling the power unit, valve means controlled by the hydraulicliquid from the inlet for controlling the application of said fluidpressure to said piston, a control plunger arranged to be moved by saidhydraulic liquid, a delivery outlet for liquid from said plunger chamberconnected to said hydraulic liquid inlet, a conduit leading from saidhydraulic inlet outside of said casing to the control plunger, saidcasing having secured thereto a head piece con-- taining said highpressure, and a hydraulic liquid cut-off valve movable apart from saidplunger, having a stationary valve seat, and operated by the firstmentioned plunger in the high pressure chamber to cut off directcommunication between the hydraulic inlet and the delivery outlet,arranged to be held open by said first mentionedv plunger.

10. A power unit comprising a cylindrical casing forming a low pressurechamber, an inlet for a fluid pressure differing from the atmosphericpressure, a piston in said chamber, having a pressure-increasing plungerconnected thereto, adapted to be moved by said pressure, a high pressurechamber for said plunger, an inlet for a hydraulic liquid forcontrolling the power unit, valve means controlled by the hydraulicliquid from the inlet for controlling the application of said fluidpressure to said piston, a control plunger arranged to be moved by saidhydraulic liquid, a delivery outlet for liquid from said plunger chamberconnected to said hydraulic liquid inlet, a conduit leading from saidhydraulic inlet outside of said casing to the control plunger, a fluidpressure pipe outside said casing leading from one end of said casing atone side of the movable wall to said valve means on the other side ofthe movable wall, said casing having secured thereto a head piececontaining said high pressure chamber, and a hydraulic liquid cut-01fvalve movable apart from said plunger, having a stationary valve seat,and operated by the first mentioned plunger in the high pressure chamberto cut oii direct communication between the hydraulic inlet and thedelivery outlet, arranged to be held open by said first mentionedplunger.

11. A power unit comprising a cylindrical casing forming a low pressurechamber, an inlet for a. fluid pressure differing from the atmosphericpressure, a piston in said chamber, having a pressure-increasing plungerconnected thereto, adapted to be moved by said pressure, a high pressurechamber for said plunger, an inlet for a hydraulic liquid forcontrolling the power unit, valve means controlled by the hydraulicliquid from the inlet for controlling the application of 14 said fluidpressure to said piston, a control plunger arranged to be moved by saidhydraulic liquid, a deliveryoutlet for liquid from said.

plunger chamber connected to said hydraulic liquid. inlet, a conduitleading .from said hydraulic inietoutside of said casing to the controlplunger, said casing having secured thereto a head piececontaining saidhigh pressure, and a hydraulic; liquid cut-off valve movable apart fromsaid plunger, having a stationary valve seat, and Operated: by the firstmentioned plunger in the high pressure chamber to cut oif directcommunication between the hydraulic inlet and the delivery outlet,arranged to be held open by said first mentioned plunger or held closedby fluid pressure.

12. A power unit comprising a cylindrical casing. forming a low pressurechamber, an inlet for a fluid pressure differing from the atmosphericpressure, a piston in said. chamber, having a pressure-increasingplunger connected thereto, adapted to be moved by said pressure, a highpressure chamber for said plunger, an inlet for a hydraulic liquid forcontrolling the power unit, valve means controlled by the hydraulicliquid from; the-inlet for controlling the application of said fluidpressure to said piston, a control plunger arranged to be moved by saidhydraulic liquid, a delivery outlet for liquid from. said plungerchamber connected to said hydraulic liquidiinlet, a conduit leading fromsaid hydraulicv inlet outside of said casing to the control plunger, afluid pressure pipe outside said casing leading fromone end of saidcasing at one side of the movable wall to said valve means on the other1 side of the movable wall, said casing having secured thereto aheadpiece containing said high pressure chamber, and a hydraulic liquidcut-oft valve movable apart from said plunger, having a stationary valveseat, and operatedby the first mentioned plunger in the high pressurechamber to cut off direct communication between the hydraulic inlet'andthe delivery outlet, arranged to be held open by said first mentionedplunger or held closed by fluid pressure.

13. A power unit comprising a cylindrical cas-- ingf'ormi'ng a lowpressure chamber, an inlet for a fluid pressure difiering from theatmospheric pressure, a piston in said chamber, having apressure-increasing plunger connected thereto, adapted to be moved bysaid pressure, a high pressure chamber for said plunger, an inlet for ahydraulic liquid for controlling the power unit, valve means controlledby the hydraulic liquid from the inlet for controlling the applicationof said fluid pressure to said piston, a control plunger arranged to bemoved by said hydraulic liquid, .a deliveryoutlet for liquid from saidplunger-chamber connected to said hydraulic liquid inlet, a conduitleading from said hydraulic liquid inlet outside of said casing to thecontrol plunger, said casing having secured thereto a head piececontaining said high pressure, and a hydraulic liquid cut-01f valvemovable apart from said plunger, having a'stationary valve seat, andoperated by the first mentioned plunger in the high pressure chamber tocut off direct communication between the hydraulic inlet and thedelivery outlet, arranged to be held open by said first mentionedplunger or held closed by fluid pres-'- sure, said cut-01f valve havinga valve seating spring.

' 14. A power uni-t comprising a cylindrical casing'forming a lowpressure chamber, an inlet for a fluid pressure differing from theatmospheric pressure, a piston in said chamber, having apressure-increasing plunger connected thereto, adapted to be moved bysaid pressure, a high pressure chamber for said plunger, an inlet for ahydraulic liquid for controlling the power unit, valv meansv controlledby the hydraulic liquid from the inlet for controlling the applicationof said fluid pressure to said piston, a control plunger arranged to bemoved by said hydraulic liquid, a delivery outlet for 7 liquid from saidplunger chamber connected to said hydraulic liquid'inlet, a conduitleading from said hydraulic inlet outside of said casing to the controlplunger, a fluid pressure pipe outside said casing leading from one endof said casing at one side of the movable wall to said valve means onthe other side of the movable wall, said casing having secured thereto ahead piece containing said high pressure chamber, and a hydraulic liquidcut-ofi valve movable apart from said plunger, having a stationary valveseat, and operated by the first mentioned plunger in the high pressurechamber to cut off direct communication between the hydraulic inlet andthe delivery outlet, arranged to be held open by said first mentionedplunger or held closed by fluid pressure, said cut-off valve having avalve seating spring.

15. A power unit comprising a cylindrical casing forming a low pressurechamber, an inlet for a fluid pressure differing from the atmosphericpressure,'a piston in said chamber, having a pressure-increasing plungerconnected thereto, adapted to be moved by said pressure, a high pressurechamber for said plunger, an inlet for ahydraulic liquid for controllingthe power unit, valve means controlled by the hydraulic liquid from theinlet for controlling the application of said fluid pressure to saidpiston, a control plunger arranged to be moved by said hydraulic liquid,a delivery outlet for liquid from said plunger chamber connected to saidhydraulic liquid inlet, a conduit leading from said hydraulic inletoutside of said casing to the control plunger, said casing havingsecured thereto a head piece containing said high pressure, andahydraulic liquid cut-01f valve movable apart from said plunger,having astationary valve seat, and oper-' ated by the first mentioned plunger inthe high pressure chamber to cut off direct communication between thhydraulic inlet and the delivery outlet but to open said communicationwhen the inlet exceeds the power pressure.

16.-A power unit comprising a cylindrical casing forming a low pressurechamber, an inlet for a fluid pressure differing from the atmosphericpressure, a piston in said chamber, having a pressure-increasing plungerconnected thereto, adapted to be moved by said pressure, a high pressurechamber for said plunger, an inlet for a hydraulic liquid forcontrolling the power unit,

valve means controlled by the hydraulic liquid from the inlet forcontrolling the application of said fluid pressure to said piston, acontrol plunger arranged to be moved by said hydraulic liquid, adelivery outlet for liquid from said plunger chamber connected to saidhydraulic liquid inlet, a conduit leading from said hydraulic inletoutside of said casing to the control plunger, a fluid pressure pipeoutside said casing leading from one end of said casing at one side ofthe movable wall to said valve means on the other side of the movablewall, said casing having secured thereto a head piece containing saidhigh pressure chamber, and a hydraulic liquid cutoff valve movable apartfrom said plunger, having a stationary valve seat, and operated by thefirst mentioned plunger in the high pressure chamber to cut 011 directcommunication between the hydraulic inlet and the delivery outletbut toopen said communication when the inlet pressure exceeds the powerpressure.

17. A power unit comprising a cylindrical casing forming a low pressurechamber, an inlet for a fluid pressure differing from the atmos-- phericpressure, a piston in said chamber, having a pressure-increasing plungerconnected thereto, adapted to be moved by said pressure, a high pressurechamber for said plunger, an inlet for a hydraulic liquid forcontrolling the power unit, valve means, located together with saidhydraulic inlet beyond the end of the plunger and controlled by the,hydraulic liquid from the inlet for controlling the application of saidfluid pressure to said piston, a control plunger arranged to be moved bysaid hydraulic liquid, a delivery outlet for liquid from said plungerchamber connected to said hydraulic liquid inlet, and a hydraulicconduit leading from said hydraulic inlet outside of said piston to thecontrol plunger, said casing having secured thereto a head piececontaining said high pressure chamber, said hydraulic head piececarrying, located beyond one end of the pressure increasing plunger,said inlet, delivery outlet and a connection for said conduit.

18. A power unit comprising a cylindrical casing forming a low pressurechamber, an inlet for a fluid pressure differing from the atmosphericpressure, a piston in said chamber, having a pressure increasing plungerconnected thereto, adapted to be moved by said pressure, a highpressurechamber for said plunger, an inlet for a hydraulic liquid forcontrolling the power unit, valve means, located together with saidhydraulic inlet beyond the end of the plunger and controlled by thehydraulic liquid from the inlet for controlling the application of saidfluid pressure to said piston, a controlplunger arranged to be moved bysaid hydraulic liquid, a delivery outlet for liquid from said plungerchamber connected to said hydraulic liquid inlet, a hydraulic conduitleading from said hydraulic inlet outside of said piston to the controlplunger, and a fluid pressure pipe outside said casing leading from oneend of said casing at one side of the movable wall to said valve meanson the other side of the movable wall, said casing having securedREFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,847,604 Finsen Mar. 1, 19322,032,185 Sciaky Feb. 25, 1936 2,235,858 Williams Mar. 25, 19412,252,482 Gates Aug. 12, 1941 2,260,490 Stelzer Oct. 28, 1941 2,260,492Stelzer Oct. 28, 1941 2,353,755 Price July 18, 1944 2,382,444 RockwellAug. 14, 1945 2,448,464 Rockwell Aug. 31, 1948

